This achievement requires that you completely solve 100 Irregular Shapes. Irregular shapes are the odd-shaped colored areas that appear in some Daily Challenges. Each time you completely and correctly fill a shape (with the numbers 1-9) and the shape flashes, that counts as one irregular shape. This will undoubtedly unlock in your trek to earning the badges, but if you want to get it out of the way, load up an Irregular Shape Daily Challenge and repeatedly complete it. If the challenge is of a lower difficulty, this will take less than one hour total.